(−) Modafinil, (−) benzhydrylsulfinylacetamide, is a psychotropic agent, used in the treatment of idiopathic narcolepsy.
According to U.S. Pat. No. 4,927,855, its preparation comprises:
a) oxidation of benzhydrylthioacetic acid to give (±) benzhydrylsulfinylacetic acid; b) reaction of this with (−) α-methylbenzylamine to give (−) α-methylbenzylamine (−) benzhydrylsulfinylacetate; c) conversion of this to (−) benzhydrylsulfinylacetic acid; and finally d) amidation to obtain (−) benzhydrylsulfinylacetamide. A key intermediate in this preparation is (−) benzhydrylsulfinylacetic acid. According to the above described process, the yield in the key intermediate is approx. 40%, with an approx. 99% enantiomeric excess.
There is therefore a need for an alternative synthesis of (−) benzhydrylsulfinylacetic acid, which can be used industrially and provides higher yields.